In the application of labels to containers having curved surfaces, such as carbonated beverage containers of glass or plastic, it has been common to wrap a label of shrinkable material about the generally cylindrical sidewall of a container and then shrink the label about the container. It has also been common to have the label be wrapped about a curved shoulder or heal surface of the container as well as the cylindrical sidewall and then be shrunk thereon. Methods and apparatus have been used wherein adhesives or solvents are applied to the leading edge and trailing edge of the label as shown, for example, in U.S. Pat. Nos. 4,574,020, 4,632,721, 4,671,836, 4,724,029, 4,729,811 and 4,844,760.
However, where the portion of the container to which the label is to be applied is curved and has a narrow vertical height relative to the height of the sidewall, it has been found that it is difficult to wrap the narrow label about the curved portion of the container in an apparatus that handles many containers per minute. The leading and trailing edges tend to overlap in a skewed relationship. The problem is even more acute where the curved portion of the container has a compound curvature and the portion of the container with the greatest diameter is not centrally located with respect to the upper edge and lower edge of label.
Accordingly, among the objectives of the present invention are to provide a method of applying a narrow shrinkable label by wrapping the label about a curved portion of a container and holding the label for sufficient time to permit shrinking the narrow label into conformity with the curved portion; wherein the container may have a compound curved portion and which method provides a uniform shrinkage about the compound curved portion with the upper and lower edges of the narrow label being in conformity thereto.
In accordance with the invention a method is provided for applying a label to a container which includes an intermediate curved portion of the sidewall thereof, which may have a compound curvature, wherein the vertical height of the curved portion is a minor portion of the entire height of the container. A narrow rectangular label of shrinkable material is first provided with a continuous or interrupted longitudinally extending strip of adhesive extending intermediate the longitudinal edges of the label at the area of the label which is to contact the portion of greatest diameter on the curved portion of the container. The strip of adhesive material is shorter than the length of the label so that the adhesive material does not contact the overlapping edges of the label. The label is wrapped about the compound curved portion with the adhesive strip engaging the curved portion of the container at the area of greatest diameter. The edges are overlapped and bonded and the overlapped label is then shrunk into position by moving the container and label through an oven. The bonding of the edges may be by adhesive, solvent or heat sealing. If adhesive or solvent is used as a bonding agent, it is applied to the only trailing edge of the label.